Someone said to me what a great lens this was and assured me it would fit the 645DF - I'd only just taken delivery of the camera and it was all new to me and f1,9 souned great. of course it doesn't fit it. I paid $AUD400 and the postage from the US!

The 80 lens has a completely different mount, smaller, no gold contacts and a pin that goes into the camera mount. Any light anyone can shed most welcome. All my research indicated it should fit. It is the one on the left, one of my other lenses that fits on the right.

Ah OK, my bad; It's just that the 35mm bayonette looked so much bigger… I just realized that due to the size difference, the rear of the 35mm is closer to the camera, and hence looks bigger due to perspective.

Anyway, "N" should not have anything to do with it. All Mamiya 645 lenses share the same 63.3 mm bayonette mount.

If it won't fit (does it fit but not turn? Not turn fully? Won't even fit?), then perhaps there's a physical defect with the 80/1.9, such as a bent flange, protruding screw, etc. Try to identify what is causing the snag.

Ah OK, my bad; It's just that the 35mm bayonette looked so much bigger… I just realized that due to the size difference, the rear of the 35mm is closer to the camera, and hence looks bigger due to perspective.

Anyway, "N" should not have anything to do with it. All Mamiya 645 lenses share the same 63.3 mm bayonette mount.

If it won't fit (does it fit but not turn? Not turn fully? Won't even fit?), then perhaps there's a physical defect with the 80/1.9, such as a bent flange, protruding screw, etc. Try to identify what is causing the snag.

It is too small for the lens socket in the front of the camera by about 1cm across the diameter. I feel as though I am going insane. I can't have a 645DF that's different to everyone else's. The other lenses I bought fit fine. WTF is going on!

That is a great lens, in fact it is my favorite. It is worth your effort to get to the bottom of this.

Are all the other lenses you use on this camera the newer sort, with autofocus and electronic aperature control? Realize that this lens was for the first generations of 645 and had none of that stuff.

Yes, and that was what I didn't realise. I told the seller what camera I had, asked on forums (not here unfortunately!) and was assured I could use this on the digital onlly 645DF. What is a fair price to ask for it? I am going to lose money I think. Not worth sending it back to the seller as it was an international purchase.